The present invention relates generally to a method and apparatus for measuring the position of an object, and more specifically to a fluorescent optical position sensor that relies on the absorption and attenuation of fluorescent light carried inside of a fluorescent waveguide to determine the position of an object.
Non-electrical position sensors are desirable for use in hazardous environments, e.g., for measuring the liquid level in gasoline or jet fuel tanks. All-optical position sensors based on the use of fiber optics would be an attractive choice because they would introduce no electrical energy, be insensitive to electromagnetic interference, have few moving parts (if any), and could provide continuous measurements.
Large-scale rotary drilling for oil and gas, minerals, and water wells, have a need for measuring the depth of drill bits and pipe segments. Measuring the length of a cable played out is inaccurate because under heavy loads the cable stretches. An auxiliary cable under minimal tension has been used, but it can interfere with the drilling operation and is generally considered to be undesirable. Hence, a need exists for a long-range (greater than 10 meters), non-contact, simple, cheap, reliable, compact, non-electrical, and robust (able to withstand drilling mud and debris) device for measuring the height above ground of the “block” that supports the drill motor that turns the drill bit during drilling.
Against this background, the present invention was developed.